Alternative activation genes are induced by treatment of microglia with IL4 or IL-13. BV2 cells were treated with IL-4 or IL-13 for 24 hrs and the mRNA expression levels for AG1 (Panel A); MRC1 (Panel B); FIZZ and YM1 (Panel C) were determined using quantitative RT-PCR. mRNA levels for each of these genes significantly increased compared to untreated alone. IL-4 or IL-13 treatment failed to induce TNFα (Panel D) or NOS2 (Panel E) mRNA expression. To determine if the alternative activation genes were induced by classical activation agents, cells were treated with IFNγ (panels A-C). In this case, no induction was observed with IFNγ treatment and, with the exception of AG1 (A), treatment of BV2 cells with the combination of IFNγ and IL-4 reduced mRNA expression of each gene studied; Panel F- Primary microglia obtained from neonatal mouse cortex also demonstrated increased mRNA expression for alternative activation genes (AG1; MRC1) on stimulation with IL-4. NOS2 was not increased by IL-4 treatment but was increased with IFNγ treatment. * = p < 0.001 compared to IL-4 treated alone; ** = p < 0.001 compared to IFNγ treated alone; *** = p < 0.001 compared to untreated alone.